Method for producing biodiesel from algal lipid with dimethyl carbonate

ABSTRACT

The present invention relates to a method for renewable energy production using biomass, more specifically, method for producing eco-friendly biodiesel with algal lipid and dimethyl carbonate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to method for renewable energy productionusing biomass, more specifically, method for producing eco-friendlybiodiesel with algal lipid and dimethyl carbonate.

2. Description of the Related Art

Technology for renewable energy production has been developed using foodresources or waste wood as biomass sources. In recent years, renewableenergy technology utilizing algal lipid has been proposed.

Algae captures carbon dioxide from the atmosphere through photosynthesisand has ecological positive functions to remove pollutants ofeutrophication causes such as nitrogen and phosphorus in water. Inaddition, it can be obtained easily from a variety of marine andterrestrial environments in large quantities. Therefore, algae is animportant life resource in renewable energy technology, especiallybiodiesel production technology. Recently, the technology removingnutrients in the wastewater and simultaneously culturing algae has beensuggested for biodiesel production.

Conventional production method of biodiesel, a mixture of fatty acidmethyl ester (FAME), a biodiesel, uses methanol in thetransesterification reaction of algal lipid and makes glycerol asbyproduct, as shown in following [Chemistry FIG. 1].

However, as methanol and hydrophobic algal lipid are immiscible,reaction rate of the transesterification is slow. Since glycerol is notsuitable for biodiesel, additional removal step is essentially necessaryas well.

There was different technology using solvents such astetrahydrofuranare, yet, the use of these solvents was not eco-friendly.On the other hand, biodiesel production utilizing dimethyl carbonate(DMC), a eco-friendly solvent, has the advantage of producing noglycerol. The detailed reactions are described as follows:

The present inventors have already disclosed an algae Ankistrodesmusgracilis cultured in wastewater such as urban sewage or industrialwastewater (Jangho Lee and Joonhong Park, Journal of Korean Society ofEnvironmental Engineering, 33(5), 2011).

In order to overcome the said problems, new technology is desperatelyneeded to replace the existing material methanol used in thetransesterification reaction of the algal lipid.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide a methodfor producing biodiesel from algal lipid with dimethyl carbonate.

The above object of the present invention was achieved by extractingalgal lipid with DMC and transesterification reaction of the algal lipidwith DMC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is GC chromatogram of biodiesel obtained by transesterificationreaction of algal lipid with DMC.

FIGS. 2 a-b is a result showing qualitative analysis (a) andquantitative analysis (b) of biodiesel produced in the presentinvention.

FIG. 3 is recovery efficiency of algal lipid by DMC.

FIGS. 4 a-b is a result of biodiesel production depending on theconcentration of DMC (a: low concentration, b: high concentration).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a method for biodiesel production withalgal lipid and dimethyl carbonate (DMC). As DMC, an eco-friendlysolvent, is hydrophobic than methanol, hydrophobic algal lipid could bebetter mixed with DMC than with methanol. Additionally, DMC could beemployed for lipid extraction from algal biomass instead of conventionalorganic solvents such as n-hexane. Due to said properties, the presentinvention has the advantage of increase in the reaction rate oftransesterification for biodiesel production from algal lipid.

Algal biomass could be mixed with DMC by the ratio of 1:2 to 1:100(g/mL) for extracting algal lipid. Preferably, the mixture ratio ofbiomass:DMC is 1:20 (g/mL).

Algal resources for the present invention are capable of being culturedin wastewater having high lipid content. More specifically, the algalresources could be selected from the genus Ankistrodesmus, the genusScenedesmus, the genus Chlorella, the genus Anabaena, the genusOscillatoria, the genus Botryococcus, the genus Neochloris, the genusTetraselmis, the genus Porphyridium, the genus Phaeodactylum, the genusNannochloropsis, the genus Ellipsoidion, the genus Isochrysis, the genusPavlova, the genus Thalassiosira, the genus Skeletonema, the genusChlorococcum, the genus Dunaliella, the genus Aphanizomenon, the genusHaematococcus, the genus Crypthecodinium and the genus Shizochytrium.

Hereinafter, the present invention will be described by the followingexamples in more detail. However, such examples are only to illustratethe invention and they do not restrict the present invention.

Example 1 Extraction and Transesterification Reaction of Algal Lipidwith DMC

Ankistrodesmus gracilis SAG278-2 cultured in wastewater was utilized toextract algal lipid.

Fatty acid methyl esters (FAMEs) obtained from conventional 2-stepsproduction process, which was hexane extraction/methanoltransesterification, and the present invention, which was DMCextraction/DMC transesterification, were analyzed by Gas Chromatography(GC)-Flame Ionized Detector (FID).

The biomass 0.5 g of Ankistrodesmus gracilis SAG278-2 was finely choppedusing a mortar. In order to extract the algal lipid, 10 mL of DMC wasadded into the above chopped algae and then mixed thoroughly for 2hours. The mixture ratio of the biomass:DMC was 1:20 (g/mL). Afteradding 0.6% of H₂SO₄ (DMC:H₂SO₄, v/v) into DMC phase obtained from saidextraction step, the DMC phase was reacted for 8 hours at 75° C. andthen it was neutralized by pH 7.5 with 1M NaOH. To remove water left inthe DMC phase, 3 g of Na₂SO₄ was added, and salt and residual sedimentformed were filtered with Filter paper (Whatman No. 41). Afterevaporating DMC left, the algal biodiesel 0.194 g was obtained.

As shown in FIG. 1, glycerol carbonate and glycerol dicarbonate asbyproducts were produced by transesterification reaction of the algallipid with DMC. This indicated that the eco-friendly solvent DMC waseffective in transesterification reaction.

FIGS. 2 a and 2 b represent FAMEs composition and those quantitativeanalysis, respectively. Compared the DMC biodiesel to the conventionalmethanol biodiesel, FAMEs composition of the DMC biodiesel was similarto the composition of the methanol biodiesel, showing comparableproperties of both biodiesels (FIG. 2 a).

Meanwhile, the conventional methanol biodiesel produces glycerol asbyproduct in the transesterification reaction so that the glycerol needsto be separated and refined. However, glycerol carbonate and glyceroldicarbonate obtained from the transesterification reaction of algallipid by DMC increased the yield of FAMEs without significant changes inbiodiesel properties (FIG. 2 b).

That is, the present invention found that the eco-friendly DMC could beapplicable to not only algal lipid extraction but alsotransesterification reaction. Therefore, biodiesel produced from algallipid with DMC has effects of more eco-friendly and fast productionprocess compared to the conventional methanol biodiesel.

Example 2 Test of Lipid Content by DMC Extraction

To examine the lipid content by DMC extraction, Chlorella vulgarisAG10032 was used to extract the algal lipid. 1 g freeze-drying biomassof said algae was mixed with 10 mL DMC or hexane and then extracted for2 hours.

As shown in FIG. 3, lipid content of the biomass was 6.84% for hexaneextraction and 5.72% for DMC extraction. As a result, the solvent DMCshowed a comparable effect with the solvent hexane which is one ofavailable lipid extracting solvents.

Example 3 Test of Transesterification Rate of Algal Lipid by DMC

Using the above algae Chlorella vulgaris AG10032, the yield of DMCbiodiesel was examined in time dependent manner. For this example, theconventional method used hexane for lipid extraction and methanol forthe transesterification reaction.

As shown in FIG. 4 a, the yield of the two types of biodiesel had nosignificant difference depending on the time at low concentration ofcatalyst (1.25%) even though the yield of methanol biodiesel was high at5 min and the yield of DMC biodiesel was high at 30 min. However, asshown in FIG. 4 b, the biodiesel yield appeared distinctly at highconcentration of catalyst (2.5%). That is, methanol biodiesel showedhigh yield at 5 min yet DMC biodiesel had high yield at 30 min.Consequently, it was revealed that transesterification rate of the DMCbiodiesel was slower than the rate of the methanol biodiesel within theinitial 5 min, however faster within 30 min after 5 min as the reactionwas completed.

What is claimed is:
 1. A method for producing biodiesel from algal lipidwith dimethyl carbonate.
 2. The method of claim 1, wherein the algallipid is extracted from an algae with dimethyl carbonate.
 3. The methodof claim 1, wherein the biodiesel is made by transesterificationreaction of algal lipid and dimethyl carbonate.
 4. The method of claim2, wherein the algae is cultured in wastewater.
 5. The method of claim2, wherein the algae is selected from the genus Ankistrodesmus, thegenus Scenedesmus, the genus Chlorella, the genus Anabaena, the genusOscillatoria, the genus Botryococcus, the genus Neochloris, the genusTetraselmis, the genus Porphyridium, the genus Phaeodactylum, the genusNannochloropsis, the genus Ellipsoidion, the genus Isochrysis, the genusPavlova, the genus Thalassiosira, the genus Skeletonema, the genusChlorococcum, the genus Dunaliella, the genus Aphanizomenon, the genusHaematococcus, the genus Crypthecodinium and the genus Shizochytrium. 6.The method of claim 2, wherein the algal lipid is extracted by themixture ratio of algal biomass:dimethyl carbonate=1:20 (g/mL).
 7. Abiodiesel without glycerol, produced according to the method of claim 1.